Method and apparatus for displaying body sounds and performing diagnosis based on body sound analysis

ABSTRACT

A lung sound diagnostic system for use in collecting, organizing and analyzing lung sounds associated with the inspiration(s) and expiration(s) of a patient. The system includes a plurality of transducers that may be placed at various sites around the patient&#39;s chest. The microphones are coupled to signal processing circuitry and A/D converters which digitize the data and preferably provides the digital data to a computer station. A data collection and organization program, executing on the computer station, organizes and formats the data into a combination display for display or printing. The combinational display includes at least two display elements. In a first display element, the data is shown for both inspiration and expiration combined in a first time scale. In a second display element, the data for inspiration and expiration are shown individually in a second time scale that is time-expanded relative to the first time scale. The system may also include application programs for detecting and classifying abnormal sounds. The resulting information may be displayed in a variety of formats to facilitate diagnosis. Additionally, the system may include an analysis program for comparing selected criteria corresponding to the detected abnormal sounds with predefined thresholds in order to provide a likely diagnosis.

This application is a divisional of application Ser. No. 10/080,209titled METHOD AND APPARATUS FOR DISPLAYING LUNG SOUNDS AND PERFORMINGDIAGNOSIS BASED ON LUNG SOUND ANALYSIS, filed on Feb. 21, 2002, now U.S.Pat. No. 6,790,183 which is a continuation-in-part of application Ser.No. 09/699,546, filed Oct. 30, 2000, now U.S. Pat. No. 6,394,967, whichis a continuation of application Ser. No. 09/172,343, filed Oct. 14,1998, now U.S. Pat No. 6,139,505.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to non-invasive diagnosticsystems and techniques, and more specifically, to a method and apparatusfor diagnosis based upon the review and analysis of body sounds.

2. Background Information

Since the time of its invention in the early 1800's, the stethoscope hasbeen used routinely by physicians to amplify sounds in the human body.The physician typically places the chest piece of the stethoscopeagainst the patient's skin and listens through the stethoscope'searpieces. By monitoring a patient's breathing, a physician may detectthe existence of adventitious (i.e., abnormal and/or unexpected) lungsounds. The identification and classification of adventitious lungsounds, moreover, often provides substantial information about pulmonaryand associated abnormalities.

Adventitious lung sounds may be classified into two major types:crackles (or rales), which are discontinuous (i.e., interrupted) sounds,and wheezes and rhonchi, which are continuous. Crackles may be furtherclassified as coarse, medium or fine, depending on their frequency,characteristics and amplitude. Wheezes may be similarly classified assibilant or sonorous. An experienced and knowledgeable physician,moreover, may be able to diagnose certain pulmonary diseases, such aspneumonia, asthma, etc., simply by detecting, identifying and noting thelocation of particular adventitious lung sounds.

Lung sounds may also be recorded and displayed to assist in thedetection and identification of adventitious sounds. For example, U.S.Pat. No. 3,990,435, entitled BREATH SOUND DIAGNOSTIC APPARATUS toRaymond L. H. Murphy, Jr., the inventor herein, discloses a system forproviding a time-expanded visual display of lung sounds. That is, thetime scale of the tracing or waveform detected by a microphone, normallyplotted at approximately 25-50 mm/sec. by standard medical strip charts,is expanded to approximately 800 mm/sec. Expanding the time scale of thewaveform significantly improves the physician's ability to detect andidentify adventitious sounds.

Devices to analyze recorded lung sounds are also known. For example,U.S. Pat. No. 5,010,889, entitled INTELLIGENT STETHOSCOPE to Bredesen etal., discloses a stethoscope capable of digitizing and storing bodysounds, including heart and lung sounds, in a memory structureconfigured to store up to six different sounds. The stethoscope includesa single chest piece with a microphone, which may be moved to one of sixlocations around the patient's chest. The stethoscope further includes aliquid crystal display (LCD) panel for displaying the waveform of arecorded sound.

Using waveform signature analysis, each of the six recorded waveforms isexamined to determine the presence of high-pitch sounds which maycorrespond to fine crackles or low-pitch sounds which may correspond tocoarse crackles. The presence or absence of these sounds is then formedinto an array that may be compared with pre-recorded arrayscorresponding to known conditions, e.g., normal lung sounds, pneumonia,etc. If a match is found between the recorded waveforms and one of thepre-recorded arrays, a diagnosis may be displayed on the LCD panel ofthe stethoscope.

Although Bredesen's intelligent stethoscope represents an improvement indiagnostic tools, especially for physicians lacking extensive experiencein detecting and identifying adventitious lung sounds, it nonethelesshas several disadvantages. First, the intelligent stethoscope has only asingle microphone, so that obtaining recordings at multiple locations istime-consuming. A single microphone also makes it impossible to record agiven sound (e.g., a particular inspiration or expiration) from morethan one point on the chest. Second, the small LCD panel is capable ofdisplaying only a single waveform in one predefined format and isprovided simply to determine whether valid data has been obtained. Dueto these limitations, the intelligent stethoscope is not that likely toprovide accurate diagnoses.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved methodand apparatus for facilitating the diagnosis of certain diseases basedupon recording, review and analysis of body sounds.

It is a further object of the present invention to provide an improvedmethod and apparatus that provides the diagnostician with a richer, morefully coordinated set of data for rapidly and accurately detecting bodysound abnormalities.

Another object of the present invention is to provide a systemconfigured to generate graphical displays of detected abnormal bodysounds to facilitate diagnosis.

A still further object of the present invention is to provide a systemfor automatically providing an accurate diagnosis based upon an analysisof recorded body sounds.

Briefly, the invention relates to a system for recording, displaying andanalyzing body sounds to facilitate the diagnosis of various diseases.The system includes a plurality of transducers, such as microphones,that may be placed at preselected sites around a patient's chest. Thetransducers detect the sound or vibration of the body at these sites.The system also includes signal processing circuitry for conditioningand converting analog signals generated by the transducers into digitaldata. Additionally, the system includes a computer station coupled tothe signal processing and digitizing circuitry. The computer stationincludes a processor, input/output circuitry, a data storage device, atleast one input device, such as a keyboard or a mouse, and a graphicaluser interface. The system may further include a printer. Executing onthe computer station is a first application program that collects andorganizes the data for display on the graphical user interface and/orfor printing.

More specifically, a plurality of transducers are preferably utilizedsimultaneously to obtain sound information from the patient. In responseto the patient's inspiration and expiration, each transducer generatesanalog signals that are conditioned and digitized by the signalprocessing circuitry and stored by the computer station at the datastorage device. The first application program organizes the receiveddata from all sites for simultaneous display on the graphical userinterface and/or printing in multiple time scales preferably in avertical stack arrangement, such that all of the information may bereviewed concurrently by an attending physician. The first applicationprogram may also display the data in frequency versus time format. Inaddition, by comparing the displayed or printed combinational data withpredefined criteria or guidelines, an accurate diagnosis may be reached.

In a further embodiment of the present invention, a second applicationprogram, also executing on the computer station, analyzes the datarecorded by the transducers. In particular, the second applicationprogram preferably includes means for identifying and counting thenumber and time of occurrence of adventitious sounds, such as wheezes,rhonchi and crackles, and categorizing the identified crackles as fine,medium or coarse. The second application program may also include meansfor performing other quantitative analysis, such as the ratio ofduration of inspiration to expiration and statistical analysis of theintensity of the recorded sounds. This information may then be providedto the attending physician in a variety of ways. For example, it may bedisplayed in tabular format or graphically in relation to the point onthe patient's chest at which the abnormal sound occurred.

A third application for generating a possible diagnosis may also beincluded. The third application may be a data analysis program, such asa neural network module or a statistical analysis module using multiplelogistic regression models, that interoperates with a database ofpre-classified lung sounds. Specifically, the database preferablyincludes multiple data sets for normal lungs sounds and lung soundsassociated with specific diseases, such as COPD, asthma, and IPF. Thedatabase may be used to train a neural network classifier or to performa statistical classification. The neural network module analyzes variousquantities computed from the patient's lung sounds in view of thetraining database and, if a match of sufficient reliability is found,presents a preliminary diagnosis and corresponding probability.

A fourth application for automatic localization of the origin ofadventitious and normal sounds may also be included. Preferably, thelocalized sounds are displayed in three-dimensions (3D) usingpreselected images or glyphs for the corresponding adventitious soundsthat have been detected.

In addition, sounds can be input to the patient. These input sounds canthen be detected by the plurality microphones disposed around thepatient and the information can be displayed and analyzed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of the invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings, in which:

FIG. 1 is a block diagram of a system for implementing a preferredembodiment of the present invention;

FIG. 2 is a block diagram of the computer station of FIG. 1 illustratingthe relationship of an operating system and several applicationprograms;

FIG. 3 is a flow diagram of the steps performed by a data collection andorganization application program;

FIG. 4 is a representative display of data for a single location;

FIGS. 5A and 5B are a highly schematic representation of a combinationaldisplay of information;

FIGS. 6A-C are exemplary plots of lung sound data versus timeillustrating the appearance of several adventitious sounds;

FIG. 7 is a highly schematic representation of another combinationaldisplay of information;

FIG. 8 is a flow diagram of the steps performed by an adventitious sounddetection application program;

FIGS. 9A and 9B are data plots that may be generated by the adventitioussound detection application program;

FIG. 10 is a highly schematic illustration of a graphical displayshowing the points at which abnormal sounds were detected;

FIG. 11 is a highly schematic illustration of a graphical displayshowing sound intensity levels as determined by the present invention;

FIGS. 12 and 13 are exemplary displays of lung sound data in frequencyversus time format;

FIGS. 14A-14B is a flow diagram of a preferred localization method inaccordance with an aspect of the present invention;

FIG. 15 is a highly schematic illustration of an abnormal sound segmentas detected at a plurality of microphone channels in amplitude versustime format;

FIGS. 16 and 17 are representative three-dimensional displays ofadventitious sounds in accordance with an aspect of the presentinvention;

FIG. 18 is an exemplary representation of an input sound signal inaccordance with an aspect of the present invention;

FIG. 19 is an exemplary representation of an input sound signal and adetected sound signal in amplitude versus time format; and

FIGS. 20-22 are a highly schematic illustrations of a microphonecassette in accordance with another aspect of the present invention.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

FIG. 1 is a block diagram of the lung sound recording and analysissystem 100 of the present invention. The system 100 includes a sensorsystem 101 which includes a plurality of sound transducers, such asanalog microphones 102, that may be placed at various sites around thechest or other area of a patient 104. In the preferred embodiment of theinvention, the system 100 uses sixteen different sites, of which,fifteen are located around the chest and one is located at the patient'strachea. More specifically, there is one site on the left side, one siteon the right side, two sites on the upper front chest separated by thespinal column (proximate to the top portion of the lungs), one site onthe lower right front chest, two sites on the upper back (proximate tothe top portion of the lungs), four sites in the middle back (proximateto the mid portion of the lungs), four sites at the lower back(proximate to the bottom of the lungs) and one site at the trachea. Itshould be understood that other chest sites may be utilized by thesystem 100. Furthermore, a simpler system may use nine sites, eightaround the chest and one at the trachea. The eight chest sites mayinclude two on the upper front chest (separated by the spinal column),one on each side and four on the back (two upper and two lower) eachpair separated by the spinal column.

Additionally, sixteen microphones 102, one located at each of the sites,are preferably utilized concurrently by the system 100 during the datacollection process, although fewer are shown in FIG. 1 for clarity. Thisallows the data from all sites to be collected concurrently.Nonetheless, a simpler system may utilize one microphone 102 positionedsequentially at the nine or more sites for data collection and the datacollection process repeated at each site. To isolate the microphones 102from external sounds, they may be embedded in the chest pieces ofconventional stethoscopes (not shown). The microphones 102 may also betaped or applied with suitable strapping to the patient 104 to preventdislocation or movement during the data acquisition process.

Leads 106 extending from each microphone 102 are used to connect themicrophones 102 to a signal conditioning circuit 108. In general, thesignal conditioning circuit 108 modifies the analog audio signalsgenerated by the microphones 102 in order to remove unwanted noise andboost the signal strength for subsequent digitizing. A suitable signalconditioning circuit for use in the present invention is disclosed inU.S. patent application Ser. No. 08/729,272, filed Oct. 10, 1996,entitled “Method And Apparatus For Locating The Origin Of IntrathoracicSounds,” now U.S. Pat. No. 5,884,997, the specification of which ishereby incorporated by reference in its entirety.

It should be understood that the sensor system 101 may utilize othersound transducers besides analog microphones. System 101 may use, forexample, digital microphones, one or more lasers configured to scan theselected sites, accelerometers, etc.

The outputs from the signal conditioner 108 (i.e., processed audiosignals from each microphone 102) are provided to a computer station110. The computer station 110, which may be implemented, at least inpart, using a personal computer or workstation, includes a centralprocessing unit (CPU) 112 coupled to a memory 114 and input/outputcircuitry 116 by a bidirectional bus 118. The memory 114 typicallycomprises random access memory (RAM) for the temporary storage ofinformation, including application programs and an operating system, andread only memory (ROM) for permanent storage of the computer'sconfiguration and basic operating commands. The operating systemcontrols the operations of the CPU 112. The computer station 110 alsoincludes a sound card 119 connected to a speaker 121 for generatingoutput sounds as discussed in more detail below.

The I/O circuitry 116 preferably connects the computer station 110 to adigital storage device 120, such as a disk drive or removable digitalstorage media, for storage and retrieval of data as described below. TheI/O circuitry 116 also connects the computer station 110 tocursor/pointer control and input devices, such as a mouse 122 and akeyboard 124. A window-based graphical user interface 126 and a printer130 are also preferably connected to the I/O circuitry 116 of thecomputer station 110. The input/output circuitry 116 preferably containsthe necessary hardware, e.g., buffers and adapters, needed to interfacewith the control devices 122, 124, the graphical user interface 126,printer 130, memory 114 and digital storage device 120.

The computer station 110 may be a personal computer of the IBM® seriesof computers sold by International Business Machiness or the Macintosh®series of computers sold by Apple Computer Inc. These computers haveresident thereon, and are controlled and coordinated by, operatingsystem software, such as IBM OS2®, Microsoft Windows® or Mac OS 9operating systems. It should be understood that the system 100 may alsobe implemented on other computer platforms, such as UNIX-basedworkstations manufactured and sold by Hewlett Packard Co. of Palo Alto,Calif., or hand-held computers, such as those running the Palm or Win CEoperating systems, among others.

As mentioned above, the signal conditioning circuit 108 is preferablyconnected to the computer station 110 such that the processed audiosignals from each microphone 102 are received by computer station 110.Specifically, each output of signal conditioning circuit 108 (whichpreferably corresponds to a particular microphone 102) is connected toan analog-to-digital (“A/D”) converter 132 that may be part of thecomputer station 110. The A/D converter 132 converts the processedanalog audio information into a digital data stream. The sampling rateof the A/D converter 132 is preferably greater than 8000 samples persecond and the bit rate is preferably greater than eight bits persample.

Additionally, the A/D converter 132 synchronously pairs a master timesignal from a system clock 133 which, for example, may be included inthe A/D converter 132 or be internal to the CPU 112 with the digitalaudio information corresponding to each microphone 102. The master timesignal provides a uniform time index to the signals received from themicrophones 102. The paired digital-audio/time information associatedwith each microphone 102 is then forwarded to the digital storage device120. The A/D converter 132 is preferably a multi-channel, high bandwidthdata acquisition printed circuit board, such as those manufactured andsold by Keithley Metrabyte, Inc. It should be understood that the CPU112, rather than the A/D converter 132, may pair the master clock signalto the digital audio information. It should be further understood thatdigital transducers, rather than analog microphones, may be utilized.The use of digital transducers would obviate the need for an A/Dconverter. Although the analog signal is digitized in the preferredembodiment, those skilled in the art will recognize that the analogsignal can be used as well.

FIG. 2 is a highly schematized illustration of the computer station 110illustrating the interaction of several software elements, including adata collection and organization application program 202, anadventitious-sound detection program 203, a probable-diagnosisprediction program 204, an automatic localization program 205, and anoperating system 206. The application programs 202-204 execute on thecomputer station 110. Interacting with the probable-diagnosis predictionprogram 204, moreover, is a training database 207. The applicationprograms 202-204 and the operating system 206 interact, as shown byarrows 208, 209, 211, and 212, via system calls to control theoperations of the computer station 110.

Included within the operating system 206 are system facilities,including a window manager 214 and a printer manager 216, which, interalia, implement at least some of the system calls. Lower layers of theoperating system 206 (or the computer station 110) may also includedevice drivers, such as a display driver 218 and printer driver 220.Drivers 218, 220 interface directly with hardware components, such asthe graphical user interface 126 and the printer 130, respectively.

It should be understood that computer station 110 may include additionalapplication programs. It should be further understood that the computerstation 110 may omit the adventitious-sound detection and/or theprobable-diagnosis prediction programs 203, 204.

Data Collection and Organization

In operation, the microphones 102 are preferably taped or strapped tothe patient's skin at the sixteen sites. Next, the system 100 isinitialized and the data collection and organization application program202 is preferably opened. FIG. 3 represents a flow chart of operations300 performed by the data collection and organization applicationprogram 202 (FIG. 2). As shown by block 302, the data collection andorganization program 202 first requests patient identifying information(such as name, identification number, physician, etc.), which may beentered by a system operator through the keyboard 124 or mouse 122. Thisinformation may be displayed on the graphical user interface 126 in adata collection window (not shown). Next, the patient is instructed tobreath in (inspiration) and out (expiration) several times. While thepatient breathes, lung sounds detected by the microphones 102 areconverted to audio signals and provided to the signal conditioningcircuit 108. Preferably, data is continuously received for a sufficientperiod of time (e.g., ten seconds) to ensure that useful data isobtained for at least one inspiration/expiration pair. As indicated atblock 304, the audio signals are measured, conditioned and provided tothe analog-to-digital converter 132 for digitization. The digital datafor each site is then stored at either the memory 114 of computerstation 110 or the digital storage device 120. If fewer microphones areused, they may be situated at the next location(s) and the processrepeated.

Next, the data collection and organization application program 202retrieves the data for display or printing, as shown by block 306.Specifically, the data collection and organization application program202 interacts with the operating system 206 so as to retrieve the datacorresponding to each microphone site from memory 114 or the storagedevice 120. The data for each site, which represents both inspirationand expiration combined, is preferably displayed on screen 228. Apreferred form of display is described below.

As indicated by block 308 (FIG. 3), the system operator then selects aparticular inspiration and expiration for further analysis byidentifying the corresponding starting and stopping points of theselected inspiration and expiration. Preferably, this is accomplishedwith the aid of a display formed in accordance with the presentinvention and illustrated in FIG. 4. FIG. 4 is a highly schematicrepresentation of a preferred display 400 of data obtained from sixteensites. The display 400 preferably includes a set of body maps 402-405,which illustrate the various sites at which data was recorded, and adata plot area 408, which contains an illustration of the recorded data.More specifically, the data plot area 408 includes the actual datatracings (i.e., signal tracings) obtained at each microphone 102(FIG. 1) and preferably includes a corresponding time axis 410. The datain data area 408 corresponds to both inspiration and expiration combinedand is preferably a plot of signal amplitude (e.g., millivolts ordecibels) from the microphones 102, each associated with a particularchannel number, versus time in seconds as shown by time axis 410. Itshould be understood that the display 400 may include other areas, suchas a patient data area 412, a command bar area 414 and aroot-mean-square (RMS) field 416.

To mark the starting and stopping points of the selected inspiration andexpiration, the system operator moves a pointer (not shown) associatedwith the mouse 122 across the data area 408 to the start of inspirationand executes a mouse “click” at that location, thereby associating aparticular time (based on the corresponding point on the time axis 410)with the start of inspiration. The data collection and organizationapplication program 202 preferably includes conventional means toassociate the position of the pointer with the time value verticallyaligned therewith upon execution of the mouse click. The system operatorsimilarly associates respective times with the end of inspiration andwith the starting and stopping times of expiration. The starting andstopping points for inspiration and expiration are best identified byexamining the signal or tracing recorded at the trachea microphone(i.e., microphone channel 16). In particular, inspiration is typicallyassociated with a first continuous, high amplitude segment 416 of thetrachea signal. When the amplitude of the segment 416 diminishes to nearzero, inspiration is typically at an end. Expiration is similarlyassociated with a continuous, high amplitude segment 418 that directlyfollows inspiration segment 416. When the amplitude of this secondcontinuous segment 418 diminishes to zero, expiration is typicallycomplete.

It should be understood that the data collection and organizationprogram 202 may as an alternative, or a supplement, to operatorselection, include one or more modules or routines that automaticallyidentify the starting and stopping points of inspiration and expirationin a similar fashion.

Following the identification of the starting and stopping points of aselected inspiration and expiration, the data collection andorganization program 202 proceeds to organize the corresponding data fordisplay as a function of time. In particular, as indicated by block 310(FIG. 3), the program 202 preferably plots the data corresponding toeach site for both inspiration and expiration in a time-expanded format.Execution of the time expansion function is preferably in accordancewith the description set forth in U.S. Pat. No. 3,990,435, which ishereby incorporated by reference in its entirety. Specifically, the datacollection and organization program 202 preferably generates twoincrements of time-expanded data: (i) slightly time-expanded and (ii)fully time-expanded. In particular, the data collection and organizationprogram 202 modifies a copy of the data for each site obtained at step304 so that it may be displayed or printed in a slightly time-expandedscale (e.g., on the order of 200-400 mm/sec.) and in a fullytime-expanded scale (e.g., on the order of 800 mm/sec.) in addition tothe more conventional, non-expanded time scale of around 20-50 mm/sec.As block 312 indicates, the data collection and organization program 202then displays and/or prints-out the data corresponding to inspirationand expiration for each site (which is now maintained in three formats:(i) unexpanded, (ii) slightly time-expanded and (iii) fullytime-expanded), in a common display, where it can be viewed in allformats simultaneously. Those skilled in the art will recognize thatmultiple degrees of expansion can be performed.

FIGS. 5A and 5B illustrate a highly schematic representation of apreferred combinational display or print-out 500 of lung sound datagenerated by the data collection and organization program 202. Thecombinational display 500 includes first, second and third plot elements502, 504 and 506, respectively, and a data field 508. Each plot element502, 504 and 506 includes a data or signal trace (e.g., trace 510 infirst plot element 502) of the amplitude of the detected lung sounds(vertical axis) for each microphone as a function of time (horizontalaxis). As mentioned above, the microphones 102 (FIG. 1) may beidentified by channel (e.g., channels one through sixteen) at least oneof which (e.g., channel sixteen) corresponds to the patient's trachea.Channels one to fifteen preferably represent the fifteen microphoneseach located at a different site around the patient's chest, asdescribed above. The first plot element 502 represents the lung sounddata for all inspirations and expirations over the predefined timeperiod (e.g., ten seconds) combined in an unexpanded time scale. Thatis, the data is formatted for display at approximately 20-50 mm/sec. Thetime period represented by the first plot element 502 is preferablyselected so that at least one set of inspiration and expiration data ofsufficient quality is obtained. The previously selected inspiration andexpiration are preferably enclosed within blocks located in the firstplot element 502. In particular, the selected inspiration is enclosed ina first block 512 and the selected expiration is enclosed in a secondblock 514.

Second plot element 504 represents the lung sounds corresponding to theselected inspiration as detected by each microphone in a slightlytime-expanded format. That is, the data is displayed on an approximately200-400 mm/sec. scale. Depending on the length of the selectedinspiration, second plot element 504 may comprise more than one (e.g.,two) panels 504 a and 504 b. Similarly, the third plot element 506represents the lung sounds corresponding to the selected expiration foreach microphone also in a slightly time-expanded format. Since theselected expiration was adjacent to the selected inspiration, the timescale (horizontal axis) for the third plot element 506 continues on fromthe time scale for the second plot element 504. The third plot element506 may also be represented by multiple panels, such as panels 506 a,506 b and 506 c, depending on its length. The signal tracings within thefirst, second and third plot elements 502, 504 and 506, moreover, arepreferably arranged in a vertical stack configuration relative to eachother.

The data field 508 preferably includes several computed quantities asdetermined from the selected inspiration and expiration information.More specifically, the data field 508 preferably contains aroot-mean-square (RMS) value calculated in a conventional manner foreach channel during the selected inspiration and expiration. The RMSvalues may be provided in column format adjacent to the first plotelement 502. In addition, data field 508 may include the length of timeof the selected inspiration 512 and the selected expiration 514,preferably in seconds. Data field 508 may further include other computedstatistical quantities identified as R1, R2, R3, R4, R5, R6, R7 and R8,that are of interest to the attending physician.

For example, R1 may represent the ratio of time of selected inspirationto time of selected expiration. R2 may be the ratio of R1 to the averageRMS value at the trachea during inspiration. R3 may be the ratio of theaverage RMS value during inspiration for the microphones located on thechest to the RMS value for the trachea during inspiration. R4 may be thestandard deviation of the RMS values during inspiration for all of thechannels. R5 may represent the ratio of the mean interchannelnon-homogeneity of the start of inspiration to the duration of theinspiration at the trachea. R6 may represent the ration of the meaninterchannel non-homogeneity of the end of inspiration to the durationof the inspiration at the trachea. R7 may represent the product ofinspiratory sounds root mean square (RMS) averaged between chest sitesand the duration of inspiration at the trachea (time integratedamplitude). R8 may represent the ratio of sound energy below 80 Hz tothat from 80 Hz to 800 Hz.

In a preferred embodiment, adventitious sounds, such as crackles, aresubtracted out of the signal before computation of RMS values. Thissubtraction operation is preferably performed as crackles can bedisproportionately loud, e.g., have much higher amplitudes, incomparison with the rest of the signal, thereby resulting in acalculated RMS value that is not necessarily reflective of regionalventilation.

Once the recorded data has been displayed and/or printed in the mannerillustrated in FIGS. 5A and 5B, it is preferably reviewed by theattending physician. As shown, the combinational display 500 conciselyand effectively presents the data obtained at multiple sites to theattending physician. In particular, examination of plot elements 504 and506, which represent the slightly time-expanded data, quickly revealsthe occurrence of any adventitious sounds. Further review of theseelements 504 and 506 provides detail information regarding theexistence, identity and location of the adventitious sounds. Forexample, by simply referring to the corresponding channel number, aphysician may quickly ascertain at which location an adventitious soundswas recorded. By arranging the signal tracings in a vertical stack asshown in the combinational display 500, he or she may also judge whetherthe same event produced adventitious sounds detected at more than onelocation. This may all be performed, moreover, without having to switchback-and-forth between a plurality of screens or sheets. That is, thedata collection and organization application program 202 (FIG. 2), incooperation with the operating system 206, may adjust the size of theplot elements 502, 504 and 506 so that they fit in their entirety in oneor two windows on the display screen 228 or on one or two sheets ofpaper, if printed. Moreover, the system 100 may mark the location ofdetected adventitious sounds within the second and third plot elements504 and 506, utilizing a set of abbreviations as identifiers, asdescribed below. For example, “C” stands for a coarse crackle, “M”stands for a medium crackle, “F” for a fine crackle, “W” for a wheezeand “R” for rhonchi.

By comparing the data contained within combinational display 500 withinformation indicative of various pulmonary conditions or diseases,moreover, the physician may be able to render a diagnosis with arelatively high degree of accuracy. In particular, Table 1 lists thecriteria or characteristics of lung sounds associated with four possibleconditions: normal, COPD, asthma and IPF, based on empirical studies andanalysis of numerous subjects with the indicated conditions. As shown inTable 1, for example, a normal patient's expiration should last about20% longer than his inspiration. This information, moreover, may bequickly obtained by simply reviewing the R1 value in the data field 508.For a patient suffering COPD, expiration is typically on the order of60% longer than inspiration.

TABLE 1 CHARACTERISTICS OF PULMONARY SOUND TRACINGS Normal COPD AsthmaIPF Ratio of Time Expiration 20% Expiration 60% Expiration variable ofInspiration longer than longer than typically to Time of InspirationInspiration much Expiration (on average) (on average) longer than In-spiration Distribution Relatively high Amplitude of Relatively variableof Sounds over amplitude of sounds during uniform the Patient's soundsduring Inspiration distri- Chest Inspiration, variable, but bution oflittle or no higher than sounds variation amplitude of across the insound sounds during chest, amplitude Expiration wheezes across thetypically chest present Sounds appear random broken, wheezes cracklesOccurring irregular typically typically During present presentInspiration Occurrence few wheezes and prominent many of Abnormalrhonchi wheezing, crackles Sounds During typically rhonchi typicallyInspiration and present, early may also present Expiration inspiratorybe present crackles also common

A diagram of illustrative adventitious or abnormal sounds may also beutilized by the attending physician, in combination with the informationcontained in Table 1, when reviewing combinational pulmonary display 500so as to assist in arriving at a diagnosis. FIG. 6A is an exemplary plotof lung sound amplitude (vertical axis) versus time (horizontal axis)for a plurality of microphones illustrating the appearance of crackles.FIG. 6B is a similar exemplary plot illustrating the appearance of awheeze. FIG. 6C is another exemplary plot illustrating the appearance ofType I and Type II rhonchus.

The preferred combinational display thus portrays the detected sounds sothat the presence or absence of the characteristics specified in Table Imay be ascertained. In particular, the combinational display portraysthe following information: (1) the ratio of inspiration to expiration,preferably as a percentage; (2) the distribution of adventitious soundsover the chest and their relative amplitudes; (3) the occurrence ofadventitious during inspiration and expiration; and (4) whether theadventitious sounds are crackles, wheezes or rhonchi. As shown, thepreferred display 500 provides all of this information to the attendingphysician in a coherent, efficient manner.

Nonetheless, it should be understood that other combinational displaysmay be generated by the system. For example, FIG. 7 is a highlyschematic representation of another combinational display or print-out700 of data by the data collection and organization program 202 (FIG. 2)from block 312. As shown, data from four chest regions (right back, leftback, right side and left side) is simultaneously portrayed either onthe graphical user interface 128 and/or printed preferably on a singlesheet of paper from printer 130. The combinational display 700 ispreferably divided into four sections 710-713, each corresponding to aparticular chest region at which data was obtained. Within each section710-713, moreover, may be a graphical body illustration 714 a-714 d,corresponding to the particular chest region at which the respectivedata was obtained. For example, graphical illustration 714 b, associatedwith the data in section 711, corresponds to the patient's right backregion.

Each section 710-713 preferably includes a representation of the data inmultiple time scales and formats. In particular, a first display element716 a-716 d, disposed with each section 710-713, respectively,illustrates the data obtained at each microphone for several repetitionsof inspiration and expiration combined in an unexpanded time scale. Thatis, the data is formatted for display at approximately 20-50 mm/sec. Asecond display element 718 a-718 d, similarly disposed within eachsection 710-713, respectively, illustrates the data obtained at eachmicrophone for inspiration only in a slightly expanded scale (e.g., onthe order of approximately 200-400 mm/sec.). A third display element 720a-720 d illustrates the data obtained by each microphone duringexpiration only, also in a slightly expanded scale (e.g., on the orderof approximately 200-400 mm/sec.).

A fourth display element 722 a-722 d illustrates inspiration only foreach microphone in a fully expanded time scale. That is, the data isdisplayed on an approximately 800 mm/sec. scale. A fifth display element724 a-724 d, corresponding to each section 710-713, respectively,illustrates the data for expiration only, also in a fully expandedscale. In the preferred embodiment, the first through third displayelements (i.e., elements 716, 718 and 720) are all preferably arrangedside-by-side above display element 722. Additionally, display element724 corresponding to fully expanded expiration, which is often thelongest, is preferably arranged below display element 722 and may wraparound as necessary.

Other arrangements of the display elements 716-724 forming combinationaldisplay 700 may also be employed. Nonetheless, all of the displayelements 716-724 are preferably arranged so as to be shownsimultaneously. That is, all of the display elements 716-724 arepreferably arranged to appear on the graphical user interface 128 at thesame time and/or printed on a single sheet of paper.

To ensure that the display elements 716-724 of combination pulmonarydisplay 700 are placed on the graphical user interface 128 at the sametime and/or preferably printed on a single sheet of paper, the datacollection and organization application 202 (FIG. 2), in cooperationwith the operating system 206, may adjust the size of the displayelements 716-724 so that they will fit in their entirety either on thegraphical user interface 128 or on a sheet of paper. Nonetheless, therelative relationships between unexpanded, slightly time-expanded, andfully time-expanded are preferably maintained.

The arrangement of information within the combinational display 500 or700 facilitates various disease diagnosis by highlighting theirdistinctive and identifying characteristics to the attending physician.In addition, the above-described procedure, unlike x-rays or exploratorysurgery, presents little risk or discomfort to the patient.

The data collection and organization program 202 may also display body,e.g., lung, sounds recorded from all or a portion of the sixteenmicrophones 102 in power versus frequency and time, as shown in FIGS. 12and 13. FIG. 12 illustrates a display or spectrogram 1200 for eightmicrophone channels 1202 a-h where time is on the horizontal axis,frequency is on the vertical axis and signal power is shown by colorand/or color intensity. The frequency range for each microphone channelis 0 to 500 Hz. Nonetheless, those skilled in the art will recognizethat other ranges may be displayed. The display 1200, which extends for20 continuous seconds, shows a plurality of inspirations and expirationsby the patient. An exemplary expiration is designated generally 1204 andan exemplary inspiration is designated generally 1206. The intensity ofsound at the particular frequency and time may be indicated by color.The colors preferably range from light yellow for low sound intensity todark red for high sound intensity. An attending physician can identifyabnormal sounds by simply reviewing the spectrogram 1200. For example, awheeze can be identified as a continuous high intensity band (dark red)at is about 125 Hz as seen in channel 1202 f (i.e., channel 12).

FIG. 13 is a display or spectrogram 1300 of a single channel, i.e.,channel 1202 f, corresponding to the same time period as FIG. 12. Here,the frequency range shown on the vertical axis is 0 to 1000 Hz. Thedisplay 1300 thus illustrates the frequencies in greater detail. Itshould be understood that the data collection and organization program202 may provide one or more drop down menus or buttons on the displayscreen 126 for selecting the desired display format, e.g., number ofmicrophone channels, range of time, frequency range, etc.

Adventitious-Sound Detection

In a preferred embodiment, the computer station 110 (FIG. 2) furtherincludes an adventitious-sound detection program 203, as mentionedabove. The adventitious-sound detection program 203 preferably parsesthe data recorded by each microphone 102 (FIG. 1) to identify theoccurrence of any adventitious sounds, such as crackles, wheeze orrhonchi. The adventitious-sound detection program 203 preferablyoperates in accordance with the methods and procedures described in U.S.patent application Ser. No. 406,152, titled LUNG SOUND DETECTION SYSTEMAND METHOD, now U.S. Pat. No. 5,165,417, to Raymond L. H. Murphy, Jr.,the inventor herein, which is also incorporated by reference herein inits entirety.

More specifically, the consecutive waves of each sound signal arepreferably analyzed to determine when a particular wave meetsestablished predefined amplitude and cycle period criteria. Once such awave is identified, the next adjacent waves are similarly analyzed todetermine whether they meet other predefined cycle period and/oramplitude criteria. Depending on the number of consecutive waves thatare found to meet particular period and/or amplitude requirements, theadventitious sound detection program 203 may categorize these portionsof the signal as crackles, wheeze, rhonchi, or other adventitious sound,depending on the criteria that were utilized in setting the thresholds.

For example, FIG. 8 is a flow chart of operations 800 executed by theadventitious-sound detection program 203. At block 802, the program 203first generates a corresponding amplitude threshold trace for the datasignal (i.e., signal trace) corresponding to each microphone site. Togenerate the amplitude threshold trace, the program 203 first determinesa running average amplitude trace corresponding to the absolute value ofthe signal over 600 data points (e.g., 300 data points on either side ofthe data point for which the running average is currently beingcalculated). As described above, information from the microphones 102 ispreferably sampled at 8000 data points per second. The program 203proceeds to determine the mean of the running average amplitude tracewhich is then multiplied by an amplitude threshold constant (e.g., 1.5).The amplitude threshold constant is used to distinguish adventitioussounds, such as crackles, from background lung noise. Empirical studieshave shown that an amplitude threshold constant of 1.5 is adequate todistinguish crackle events in most cases, although other values may alsobe employed. The resulting value is added to the running averageamplitude trace to form an amplitude threshold trace.

FIG. 9A is a data plot 902 for a particular microphone 102 (FIG. 1)which represents either inspiration or expiration plotted as a functionof time. The data plot 902 includes a data signal 910 and acorresponding amplitude threshold trace 912, generated as describedabove. As shown, the data signal 910 exceeds the amplitude thresholdtrace 912 at various points (e.g., points A, B, C, etc.). Theadventitious-sound detection program 203, at block 804 (FIG. 8), nextcompares the data signal 910 (FIG. 9A) to the corresponding amplitudethreshold trace 912 and, for each portion of the data that exceeds thecorresponding threshold, stores a corresponding index or identifier ofthat portion of the data.

Next, program 203 similarly identifies portions of the data signal thatexceed a signal slope threshold. Specifically, the program, at block 806(FIG. 8), generates a corresponding slope threshold trace. Morespecifically, the program 203 calculates the first difference of thedata trace using a difference equation. A preliminary slope thresholdtrace is then formed by calculating the running average over 600 datapoints. The median of the preliminary threshold trace is then determinedand the median is multiplied by a slope threshold constant (e.g., 0.15).The slope threshold constant is chosen to distinguish adventitioussounds from discrete sound artifacts (such as machine noise, skinnoises, etc.) that may be present in the signal trace and may also haverapidly rising slopes. Again, empirical studies have shown that a slopethreshold constant of 0.15 is adequate in most cases to distinguishadventitious sound events from sound artifacts. The resulting value isthen added to the preliminary threshold trace to form a slope thresholdtrace.

FIG. 9B is a data plot 920 for a particular microphone 102 (FIG. 1)plotted as a function of time. The data plot 920 includes a slope datasignal 922 and a corresponding slope threshold trace 924, generated asdescribed above. As shown, the slope data signal 922 exceeds the slopethreshold trace 924 at various points (e.g., points D, E, F, etc.).

Returning to FIG. 8, the adventitious-sound detection program 203, atblock 808, next compares the slope data signal 822 (FIG. 9B) to thecorresponding slope threshold trace 924 and, for each portion of thesignal that exceeds the corresponding threshold, stores a correspondingindex or identifier of that portion of the signal. Program 203 nextproceeds to determine the start and end of each “anomalous” signalsegment detected in steps 804 and 808 above. In particular, as shown atblock 810, for each segment of the data trace that exceeded theamplitude threshold trace, program 203 may define the end as the firstzero crossing after the last point at which the amplitude threshold wasexceeded. To determine the start, program 203 preferably locates theearliest slope exceeding point that occurs before the first amplitudeexceeding point and defines the start as the zero crossing before thelocated slope exceeding point. If no corresponding slope exceeding pointis found, the portion is not considered to be a crackle event.

After identifying the start and end of each anomalous signal segmentwithin a given signal, program 203, at block 812, is ready to furtheranalyze and classify the various signal segments. In particular, program203 may first determine the number of zero crossings that are present inthe subject anomalous signal segment. If the number of zero crossings isgreater than 4 but less than 8, program 203 next proceeds to calculatethe first three half periods of the signal portion and computes anaverage detection width as the mean of the three half period values. Ifthe third half period is longer than the second half period, thenprogram 203 preferably classifies the sound portion as a crackle. Othercriteria may optionally or additionally be used to classify soundsegments as crackles. For example, a crackle may be defined as having aninitial deflection width or a maximum deflection width that exceeds apredefined threshold or a number of sequential deflection widths thatexceed some threshold. Additionally, if the computed average detectionwidth (or the initial or maximum deflection widths) is between 0.0015and 0.0025 seconds, the sound portion is classified as a fine crackle.If the computed average detection width is between 0.0025 and 0.0035seconds, the sound portion is classified as a medium crackle and if theaverage detection width is between 0.0035 and 0.0045 seconds, the soundportion is classified as a coarse crackle.

To identify wheezes and rhonchi, program 203 preferably proceeds asfollows. First, as shown at block 814, program 203 divides theinspiratory or expiratory data signal corresponding to each site intosections, which may each be ⅛ second in duration. Next, at block 816,program 203 determines all half periods of the zero crossings of thesignal, and the mean and standard deviations of the half periods foreach section. Similarly, at block 818, program 203 determines the peakamplitudes of each half cycle and the mean and the standard deviation ofthe peak amplitudes for each segment. These measured half periods andpeak amplitudes are then compared to predefined criteria.

As indicated by block 820, if the ratio of the standard deviation ofhalf period to mean half period is less than a predefined threshold(e.g., 0.4) and, if the standard deviation of peak amplitude over meanpeak amplitude is less than another predefined threshold (e.g., 0.4),the subject segment is classified as a wheeze or rhonchus. Todifferentiate between wheezes and rhonchi, program 302, at block 822calculates the average frequency of the segment (i.e., 1/{2*mean halfperiod}) and, at block 824, compares the average frequency to apredefined threshold (e.g., 200 Hz). In particular, if the averagefrequency is less than the predefined threshold, program 203 classifiesthe segment as a rhonchus. If the average frequency is greater than 120Hz, program 203 classifies the segment as a wheeze.

It should be understood that some other predefined threshold may be usedto classify an abnormal sound segment as a rhonchus, e.g., a selectedfrequency between 100-200 Hz, such as 120 Hz.

It should be understood that other detection algorithms or techniquesmay be implemented by the system 100.

For example, a database of templates corresponding to variousadventitious sounds may be stored in the memory 114 of the system.Portions of the data signal 910 can then be compared to each of thetemplates until a match is found.

Alternatively, program 203 may be configured to look first at segmentsexceeding the slope threshold (e.g., start with blocks 806 and 808) andthen perform amplitude analysis of blocks 802 and 804. Program 203 couldalso be configured to filter out the low frequency (e.g., below 600 Hz)portion of the detected signals and designate any remaining segments asfine crackles.

Following the detection of adventitious sounds as described above, thesystem 100 may display the results to the system operator and/or theattending physician. For example, the system 100, through adventitioussound detection program 203, may label sections of the signals containedin the second and third plot elements 504 and 506 (FIGS. 5A and 5B) atwhich adventitious sounds were detected. In particular, the system 100may mark the location of detected adventitious sounds, utilizing a setof abbreviations as identifiers. For example, “C” stands for a coarsecrackle, “M” stands for a medium crackle, “F” for a fine crackle, “W”for a wheeze and “R” for rhonchi.

The system 100 may also generate additional body plots either ongraphical user interface 128 or in print form to illustrate the locationof the detected adventitious sounds. FIG. 10 is a highly schematicillustration showing the location of detected crackles, wheezes, and/orrhonchi. Specifically, a graphical depiction 1000 preferably includes aset of body plots 1002 a-1008 a for inspiration and a similar set ofbody plots 1002 b-1008 b for expiration. In particular, the body plotspreferably correspond to a patient's front 1002, right side 1004, back1006 and left side 1008 chest regions. Again, utilizing a set ofabbreviations as identifiers, the system 100 marks the location ofdetected adventitious sounds.

In addition to the body plots, the graphical depiction 1000 may alsoinclude a summary field 1010. Located within the summary field 1010 maybe information relating to the total number of fine, medium, and coarsecrackles that were detected for inspiration and expiration. The numberof crackles may be further defined as having occurred early (e.g., firstthird), mid (e.g., middle third) or late (e.g., last third) of eitherinspiration and expiration as a function of time. Similarly, the totalnumber of wheezes and rhonchi that were detected during inspiration andexpiration may also be provided within the summary field 1010 ofgraphical depiction 1000.

As mentioned above, application program 203 may further determine aroot-mean-square (RMS) level for the inspiratory and expiratory portionof the signal from each microphone. The RMS levels provide the attendingphysician with a mechanism for comparing the intensity of the lungsounds as recorded at each microphone. The computed RMS values,moreover, may be displayed on graphical user interface 128 (FIG. 1) intabular or graphical form. Referring to FIG. 11, program 203 preferablygenerates an RMS graphical display 1100 having a first set of body plots1102 a-1108 a each corresponding to a particular chest region (e.g.,front, right, back and left) for inspiration and a second set of bodyplots 1102 b-1108 b similarly corresponding to a particular chest regionfor expiration. Within each body plot 1102-1108 is a set of markers 1110each corresponding to a particular microphone site. Each marker 1110,moreover, is preferably color-coded to reflect the intensity of thecomputed RMS level for that site. A color coded scale 1112 of RMS levelsis also provided, where blue corresponds to relatively low RMS intensitylevels and red corresponds to relatively high RMS intensity levels.

Review of graphical display 1100 by the attending physician may providesubstantial information. For example, the presence of fluid in apatient's pleural space (i.e., the area between the chest wall and thelungs and against which the lungs slide) has been found to cause amarked decrease in sound intensity over the affected area. Theidentification of this condition may be rapidly and accuratelydetermined by means of a review of display 1100. In particular, areaswith relatively low RMS values (i.e., low sound intensity) are indicatedin display 1100 by blue designations 1110. Accordingly, the presence offluid in the pleural space often manifests as blue designations 1110,especially where adjacent red designations (i.e., areas of high soundintensity) are also present.

It should be understood that, for a given signal trace, separate RMSvalues may be calculated for those portions of the signal tracerepresenting adventitious sounds and those portions which do notcorrespond to adventitious sounds.

Automatic Localization of Adventitious Sounds

In the preferred embodiment, the system 100 (FIG. 1) further includes anautomatic localization program 205 (FIG. 2), which reviews the resultsobtained from the adventitious sound detection program 203 anddetermines the physical location, i.e., the coordinates, inthree-dimensions (3-D) of the point of origin of one or moreadventitious sounds that have been identified. As described herein,program 205 may also be used to automatically compute the point oforigin of normal body sounds.

FIGS. 14A-14B is a flow diagram of the preferred localization method ofthe present invention. First, an abnormal sound segment, such as acrackle, is identified on a given channel, as indicated by block 1402.Next, the start time (ts) and end time (te) of the abnormal soundsegment are identified, as indicated by block 1404. The abnormal soundsegment, from ts to te, is then cross-correlated with a slightly longerrecord from a second microphone channel, as indicated at block 1406,namely, from ts minus several milliseconds (ms) to te plus approximately40 ms. The resulting cross-correlation maximum is preferably retained,as also indicated at block 1406. This procedure is preferably repeatedfor the signals from all sites, thereby producing cross-correlationmaximums for all pairs of microphones, as indicated at block 1408. Allcross-correlation maximums are then normalized by the amplitude of theabnormal sound segment from the first channel evaluated, and compared tolocate the highest cross-correlation maximum, as indicated at block1410. The abnormal sound segment from the microphone channel having thehighest maximum correlation and the earliest start time is designated tobe the “mother” signal, while all others are designated to be “daughter”signals, as indicated at block 1412.

FIG. 15 is a highly schematic illustration of a plurality of signals ortraces 1500 a-e in amplitude versus time format showing a “mother”signal and a plurality of “daughter” signals. More specifically, signal1500 e, which has the highest energy in the relevant frequency range andthe earliest arrival time, will be designated as the “mother” signal,while the remaining signals 1500 a-d will each be designated as“daughter” signals.

Next, the mother signal and all daughters signals are cross-correlatedto compute the time delay for each daughter signal relative to themother signal, as indicated at block 1414. A three-dimensional gridhaving a plurality of points or cells is then established, as indicatedat block 1416. The grid logically encompasses all or any part of thepatient's thorax, e.g., the lungs. That is, the patient's thorax isrepresented by the grid. The grid is preferably on the order of 40centimeters (cm) wide (x), 20 cm high (y) and 20 cm deep (z). Within thegrid are a plurality of grid points with a resolution of 1 cm in allthree dimensions. The program 205 considers each grid point anddetermines the probability that the abnormal sound being evaluatedoriginated from that grid point. Specifically, for every grid point,program 205 computes the arrival time differences at each microphonelocation assuming the sound originated from the grid point currentlybeing evaluated, as indicated at block 1418 (FIG. 14B). The location ofthe sound source (i.e., the grid point under evaluation) and thelocation of the microphones are all known. In addition, program 205utilizes an assumed sound speed. Rather than using a single assumedsound speed, however, the program 205 preferably evaluates a range ofsound speeds for each grid point. In particular, arrival times arecomputed with the sound speed moved in increments of 2centimeters/millisecond (cm/ms) between the range of 2 to 12 cm/ms.

A probability that the abnormal sound originated from the grid pointbeing evaluated is then computed, as indicated at block 1420. Theprobability of the selected grid point and sound speed may be a weightedsum of the difference between the computed arrival time difference andthe measured arrival time difference for all microphone pairs. Theweight may be a corresponding correlation coefficient. The grid pointand sound speed having the highest probability is then selected as theorigin of the respective sound, as indicated at block 1422. Processingby the localization program 205 is then complete, as indicated by endblock 1424. The localization algorithm is preferably run in real-time,i.e., as the body sounds are being received by the system.

It should be understood that other methods of sound localization may beutilized.

Three-Dimensional Displays

Once the origin of the abnormal sound has been determined, thatinformation can be provided to the attending physician in a number ofways. For example, it can be displayed on the graphical user interface126. FIG. 16 is a highly schematic exemplary display 1600 oflocalization information which may be presented on the graphical userinterface 126 and reviewed by the attending physician. Display 1600 is athree-dimensional representation of at least a portion of the patient.It may include an outline or profile 1602 of a human body or a portionthereof, such as a chest area, and a plurality of parallel, horizontalimage planes 1603. In addition, left (L) 1604 a and right (R) 1604 bmarkings may be provided to indicate whether the profile 1602 is of thepatient's front or back. The profile 1602 and image planes provide apoint of reference for the location of detected abnormal sounds that arealso displayed. A plurality of numeric markings 1606, e.g., 1-7 and9-15, may be provided that correspond to the microphone sites.Microphone number “8” which is located at the patient's heart is notincluded in the display 1600.

As the previously recorded data of a patient's breathing, i.e.,inspiration and expiration, is played back, indicators or markings 1608appear at the point of origin of adventitious sounds. These markings maybe generally rectangular or they may take other shapes. Preferably, themarkings 1608 appear at the time the respective adventitious sound wasdetected and disappear shortly thereafter. For example, the color of themarkings 1608, as described below, may be faded by approximately 30%after 100 milliseconds (ms) of its first appearance. After 200 ms, thecolor may be faded by another 30% and so on until about 700 ms after themarking's first appearance at which point it is faded to about 5% of itsoriginal color. Alternatively, the color may fluctuate with theintensity of the abnormal sound, and completely disappear when theabnormal sound is no longer being detected.

The markings 1608 of FIG. 16 correspond to abnormal sounds, such ascrackles and wheezes, identified by the adventitious sound detectionprogram 203 and localized by the localization program 205. Color codingsmay be used to distinguish between crackles and wheezes. Crackles, forexample, may be illustrated by markings 1608 that range from gray toblack depending on their intensity, i.e., the number of detectedcrackles at that location or space. Black being high intensity whilegray represents low intensity. Wheezes, on the other hand, may berepresented by markings that range in color from yellow to dark reddepending on the intensity with yellow being low intensity and red beinghigh intensity. Large areas, such as the patient's lower left lung area,having many concentrated crackles may be indicative of pneumonia. On theother hand, if the crackles appear distributed widely across the lungs,especially toward the base, it may be indicative of congestive heartfailure.

This real-time, video style display can be generated from previouslyrecorded or stored data or it can be generated in real-time as thepatient breathes. FIG. 16 thus corresponds to a snap-shot of thisvideo-style playback

FIG. 17 is another exemplary three-dimensional representation 1700illustrating localization information as computed by the system 100 ofthe present invention. As shown, the display 1700 includes four areas1702 a-d. A first area 1702 a contains a front view of the patient. Thefront view includes an outline or profile 1704 of the patient andrepresentative lung images 1706 a-b. Second area 1702 b contains a backview of the patient including an outline or profile 1708. Third area1702 c contains a side view, e.g., left side, of the patient includingan outline 1710. Fourth area 1702 d contains a sectional view of thepatient at a selected elevation. It may also include a correspondingoutline or profile 1712.

Glyphs are preferably displayed within the profile displayed in eacharea 1702 a-d to illustrate and represent the detection of abnormalsounds. In the illustrative embodiment, spheres 1714 are used torepresent wheezes, while stars 1716 are used to represent crackles. Thesize of each glyph can be adjusted to reflect the number of occurrences,e.g., density, of the respective adventitious sound at that location,i.e., the larger the glyph the more adventitious sounds were detected.

It should be understood that a user may manipulate cutting planes withinthe first area 1702 a to generate the displays shown in the second tofourth areas 1702 b-d. Patient information as well as a legend may alsobe displayed. The display 1700 can be configured to show information ina static format, i.e., all abnormal sounds detected in the relevant timeperiod. Alternatively, it may be configured to show information in adynamic, real-time format, i.e., with the glyphs appearing upondetection of the respective abnormal sound and disappearing at theirconclusion. Again, a color scale may be implemented to represent soundintensity with darker colors representing higher intensities.

Those skilled in the art will recognize that other displays of abnormalsounds and their localization can be created.

Automatic Localization of Normal Sounds

The automatic localization program 205 may also be used to determine theorigin, i.e., the physical coordinates, of normal body sounds. There arebenefits to localization of normal sounds. For example, duringexpiration sounds are mostly produced in the large airways. Localizationof these sounds corresponds to the location of the large airways of apatient. Thus, adventitious sounds can be localized relative to theselarge airways.

Additionally, since sounds during inspiration are mostly producedperipherally, the location of these normal inspiratory sounds canprovide information on which areas of the lung are the best and worstventilated.

Probable-diagnosis Prediction Program

In the preferred embodiment, the system 100 (FIG. 1) further includes aprobable-diagnosis prediction program 204 (FIG. 2), which reviews theresults obtained from the adventitious-sound detection program 203 andpreferably provides a proposed diagnosis based upon those results. Thisprogram 204 may be based on a neural network module, such as the neuralnetwork programming tools from The Mathworks, Inc. or other statisticalclassification methods. The probable-diagnosis prediction program 204preferably interacts with a training database 207 to derive the proposeddiagnosis. In particular, the training database 207 preferably containsa set of adventitious lung sound data from patients previously diagnosedwith various pulmonary diseases, such as COPD, asthma, IPF, etc. Morespecifically, the training database 207 includes typical datacorresponding to the ratio of inspiration to expiration, the numbers andlocations of coarse, medium, and fine crackles, wheezes, and rhonchi,and RMS values commonly associated with these diseases. Theprobable-diagnosis prediction program 204 compares the results obtainedby the adventitious-sound detection program 203 for the given patientwith the information in the training database and provides a proposeddiagnosis, which represents the particular disease which most closelymatches the results obtained for the given patient.

It should be understood that the probable-diagnosis prediction program204 may alternatively utilize multiple logistic regression models toarrive at a proposed diagnosis. A suitable multiple logistic modelapproach is described in P. Bettencourt, E. Del Bono, D. Spiegelman, E.Hertzmark and R. Murphy, Jr. Clinical Utility of Chest Auscultation inCommon Pulmonary Diseases Vol. 150, No. 5 American Journal ofRespiratory and Critical Care Medicine (November 1994), which is herebyincorporated by reference in its entirety.

Input Sounds

Sounds may also be input to the patient in order to generate usefulinformation that can be detected by the system 100 of the presentinvention. The sounds may be patient generated or they may be externallygenerated. The externally generated sounds can be input to the patientby a mouthpiece 123 (FIG. 1) having one end connected to the speaker 121and the other end inserted into a patient's mouth. The mouthpiece 123may simply be a hollow cylinder, such as a disposable paper or plastictube. The sound enters the patients airways, travels through his or herlung tissue and is detected by the microphones 102. The properties ofthe patient's lung and other tissue through which the sound travelsbefore being detected by the microphones 102 affect the sound'scharacteristics. Depending on when and how the input sound is detectedcan provide information regarding these properties.

One parameter that can be measured, for example, is time delay. Timedelay, which refers to the amount of time it takes for the input soundto be detected at the microphones 102, is a function of the speed ofsound in the lung tissue. Speed of sound, moreover, is a function oflung characteristics such as the presence or absence of fluid, vapor,the morphology of lung tissue, etc. Also, the speed of sound is three tofifteen times faster in air than lung tissue. A patient with emphysema,moreover, typically has areas of his or her lung tissue missing, i.e.,destroyed air sacs. Therefore, a physician would often detect unusualincrease in sound speed, i.e., less time delay, in the affected areas ofsuch a patient, as the sound would be travelling through some pockets ofair rather than lung tissue.

The input sounds may be continuous, such as white noise, ordiscontinuous. FIG. 18 illustrates an example of a discontinuous inputsound signal 1802 in amplitude versus time format. The input soundsignal 1802 is preferably a hybrid of many frequencies. In theillustrative embodiment, it starts at 150 Hz and ends at 170 Hz. Morespecifically, the frequency of the input sound changes by about 10%every cycle. This varying frequency signal aids in accuratelydetermining time delay, especially when the time delay is about oneperiod.

It should be understood that an externally generated input sound may beinput to the patient at a location other than the patient's mouth. Forexample, the end of the mouthpiece may be placed at a location on thepatient's neck, chest, back or side, among other places.

Acoustic Resonance

Application of an input sound may also result in the generation ofacoustic resonance. Acoustic resonance is the continuation of sound fromwithin the body after the input sound has terminated. FIG. 19 is anamplitude versus time plot of two signals illustrating the phenomenon ofacoustic resonance. FIG. 19 includes an input sound plot 1902 and adetected sound plot 1904 that is picked up by a respective microphone102 (FIG. 1). It should be understood that the input sound plot 1902 maycorrespond to the input sound as detected by the microphone 102 locatedat the patient's trachea or it may be a plot of the actual input sound.The input sound plot 1902 begins at a selected start time T1 and isterminated at a selected end time T2. The time duration of the inputsound, i.e., T2 minus T1, is preferably on the order of 0.5 seconds. Asshown, the detected sound plot 1904 begins shortly after T1. However, insome circumstances, the detected sound plot 1904 continues well past,e.g., for several more seconds or more, the time T2 at which the inputsound is terminated. This extension or continuation of the detectedsound, which is referred to herein as acoustic resonance, is designatedgenerally by reference number 1906. As indicated, the acoustic resonance1906 extends from approximately time T2 to an end time T3.

The length of time of the acoustic resonance signal and its frequency orfrequencies can provide information regarding the condition of thepatient's lungs. For example, in normal persons, the resonance may becommonly observed at all sites. However, in patient's suffering fromemphysema, the observed resonance is significantly reduced.

Sound Sensor Cassette

In a further aspect of the present invention, a plurality of microphonesmay be embedded within a single structure to form a cassette. FIGS. 20and 21 are highly schematic illustrations of a cassette 2002 in plan andcross-section views. The cassette 2002 houses a plurality of microphones102. In the illustrative embodiment the microphones are arranged in a4×4 array that is generally square or rectangular. The cassette 2002further includes a core 2004 (FIG. 21), preferably made from foam, forsupporting the microphones 102. Specifically, recesses are formed in thefoam core 2004 to receive the microphones 102 such that the microphones102 are flush with an upper surface 2004 a of the core 2004. Leads 106from the microphones 102 preferably extend through the core 2004.

In the preferred embodiment, the cassette 2002 further includes adisposable interface 2006 that covers at least the entire upper surface2004 a. The interface is preferably formed from a hospital grade“clean-wrap”. The interface 2006 may be attached to the core 2004 of thecassette in a variety of ways, such as by tape, clips, fasteners, etc.In an alternative embodiment, the interface 2006 may surround and coverthe entire core 2004.

The cassette 2002 may be positioned on a hospital bed (not shown)between the mattress and a patient. The cassette 2002 may also be reusedby simply replacing the interface 2006. By incorporating the microphones102 within the cassette 2002, the microphones 102 can be quickly andeasily positioned to a location of interest to the attending physician.Indeed, the cassette 2002 in cooperation with the system 100 of thepresent invention can be used to locate intestinal obstructions. Suchobstructions typically generate substantial noises. Here, the cassette2002 can be easily moved to different locations on the patient'sabdomen. By using the cassette 2002 in cooperation with the localizationprogram 205 described above, the location of a patient's intestinalobstruction can be determined non-invasively. The cassette 2002 can alsobe utilized to monitor heart murmurs. In this cases, the cassette 2002is preferably placed on the patient's chest preferably near his or herheart. Again, cooperation of the microphones 102 of the cassette withthe localization program 205 allow an attending physical to pin pointthe point of origin of heart murmurs.

FIG. 22 is a perspective view of a preferred embodiment of a cassette2300 having a core structure 2302 that is preferably formed from a foam.Core structure 2302 defines a contoured upper surface 2304 and asubstantially flat lower surface 2306. Disposed with the core structure2302 are a plurality of microphones 102 a-. As with the cassette 2002 ofFIGS. 20 and 21, recesses are formed in the core 2302 to receive themicrophones 102 such that the upper portions of the microphones 102 areflush with the contoured upper surface 2304. Narrow slots 2308 arepreferably formed, e.g., cut, in the core to receive the leads from themicrophones 102. As shown, upper surface 2304 is contoured such that acentral area 2310 is recessed relative to two side areas 2312 of thecore 2302.

As with cassette 2002, cassette 2300 is preferably positioned on ahospital bed (not shown) between the mattress and a patient.Furthermore, the patient lies in either a horizontal or slightlyinclined position on the cassette, such that the patient's spine issubstantially aligned along the central area 2310, and the side areas2312 are proximate to the patient's sides. A disposable cover (notshown) may be placed over the cassette 2300 or at least upper surface2304.

Distinguishing Between IPF and CHF Based on Crackle Analysis

Crackles often occur in patients suffering from both interstitialpulmonary fibrosis (IPF) and from congestive heart failure (CHF). As thecrackles can sound very similar in both cases, it can be difficult todistinguish between the two conditions. In another aspect of the presentinvention, a system and method have been developed for differentiatingbetween the crackles produced by an IPF patient from the cracklesproduced by a CHF patient.

Generally speaking, crackles produced by a patient with CHF aretypically transmitted over a larger area of the lung(s), e.g., an areathat is roughly 4 inches by 4 inches, than the crackles of a patientwith IPF which are transmitted over a much smaller area, e.g., an areathat is roughly 2 inches by 2 inches.

In the illustrative embodiment of this aspect of the invention, theadventitious sound detection program 203 is further configured tocompute a novel value, referred to herein as the transmissioncoefficient. First, as described above, for each crackle detected duringone or more inspiration phases of a patient's breathing, the mothercrackle and corresponding daughter crackles are identified. Next, thesignal corresponding to each identified mother crackle iscrosscorrelated with the signals corresponding to the respectivedaughter signals, as described above, thereby producing acrosscorrelation function that has a peak value. Additionally, thesignal corresponding to each mother crackle is autocorrelated to producean autocorrelation function having a peak. For each set of mothercrackle and corresponding daughter crackles, program 203 calculates theratio of the peak of the crosscorrelation function to the peak of themother crackle autocorrelation function. The calculated ratios, whichcharacterize the degree of sound transmission from the sound source tothe chest, are then averaged to generate the transmission coefficient.The transmission coefficient has a value of 0% in the absence of anytransmission of the adventitious sound beyond the one location orchannel at which it is detected and 100% when there is equaltransmission to all locations or channels.

In the illustrated embodiment, the adventitious sound detection program203 is further configured to display a calculated transmissioncoefficient, which can be used by an attending physician in arriving ata diagnosis.

Furthermore, as indicated above, each crackle detected by program 203has a corresponding frequency. In the preferred embodiment, programassociates the frequency of the mother crackle with the computedtransmission coefficient. Program 203 also computes an average cracklefrequency by averaging the frequency between all crackle families, whichis then associated with the average transmission coefficient.

Experimental tests have shown that for a given average frequency, thetransmission coefficient for a CHF patient is noticeably andstatistically higher than the transmission coefficient for an IPFpatient. A transmission coefficient higher than 0.03xF+6, where F is thefrequency in Hertz (Hz) associated with the transmission coefficientindicates a high likelihood of CHF, while a transmission coefficientlower than 0.03xF+6 indicates a high likelihood of IPF.

Accordingly, in a further embodiment, program 203 also displays atwo-dimensional plot of transmission coefficient (preferably on thevertical axis) versus frequency on the horizontal axis. The plot,moreover, is preferably separated into upper and lower halves by a linecorresponding to the following equationtransmission coefficient=0.03F+6

The position of a given calculated average transmission coefficient ontothis plot by program 203 assists the attending physician indifferentiating a CHF diagnosis with an IPF diagnosis. In particular, asmentioned above, if the position of the calculated average transmissioncoefficient falls above this line suggests CHF, while a position belowthis line suggests IPF.

The foregoing description has been directed to specific embodiments ofthis invention. It will be apparent, however, that other variations andmodifications may be made to the described embodiments with theattainment of some or all of their advantages. Accordingly, thisdescription should be taken only by way of example and not by way oflimitation. It is the object of the appended claims to cover all suchvariations and modifications as come within the true spirit and scope ofthe invention.

1. A method comprising: receiving digital data corresponding to lungsounds detected during the inspiration and expiration of a patienthaving a chest by a plurality of transducers placed at various sitesaround the patient's chest; and generating, in response to the digitaldata, a display on a graphical user interface, the display having adisplay element in which the detected lung sounds from a plurality oftransducers are plotted in a vertically stacked configuration, whereinthe detected lung sounds from at least one transducer is plotted as afunction of frequency over time.
 2. The method of claim 1 wherein thedisplay element may be one of a plurality of colors and the methodfurther comprises modifying the color of the display element to reflectintensity of a detected sound at a given time and frequency.
 3. Themethod of claim 2 wherein the sound intensity is indicated by one ormore colors.
 4. The method of claim 1 wherein in the plotted frequencyranges from approximately zero to 500 Hz.
 5. The method of claim 1,further comprising: analyzing the data to detect one or moreadventitious sounds.
 6. The method of claim 5, wherein the one or moreadventitious sounds are selected from the group consisting of: crackles,wheezes, and rhonchi.
 7. The method of claim 1, further comprising:generating a proposed diagnosis based on the data.
 8. A methodcomprising: receiving digital data corresponding to lung sounds detectedduring the inspiration and expiration of a patient having a chest by aplurality of transducers placed at various sites around the patient'schest; generating, in response to the digital data, a display on agraphical user interface, the display having a display element in whichthe detected lung sounds from a plurality of transducers are plotted ina vertically stacked configuration; and locating the approximatephysical coordinates of the detected sounds through the analysis of thesounds detected by the plurality of transducers.
 9. The method of claim8, wherein the approximate physical coordinates are three dimensional.10. The method of claim 8, wherein the display is a visual display ofsound locations on a body corresponding to the approximate physicalcoordinates.
 11. A method comprising: receiving digital datacorresponding to lung sounds detected during the inspiration andexpiration of a patient having a chest by a plurality of transducersplaced at various sites around the patient's chest; generating, inresponse to the digital data, a display on a graphical user interface,the display having a display element in which the detected lung soundsfrom a plurality of transducers are plotted in a vertically stackedconfiguration; inputting sound to the patient from an input device;monitoring a speed of the sound to reach a transducer; and determiningcharacteristics of the patient based on the speed of sound from theinput to the transducer.
 12. A method comprising: receiving digital datacorresponding to lung sounds detected during the inspiration andexpiration of a patient having a chest by a plurality of transducersplaced at various sites around the patient's chest; generating, inresponse to the digital data, a display on a graphical user interface,the display having a display element in which the detected lung soundsfrom a plurality of transducers are plotted in a vertically stackedconfiguration; inputting sound to the patient from an input device;monitoring a resonance of the sound at a transducer; and determiningcharacteristics of the patient based on the resonance of the sound atthe transducer.
 13. A method comprising: receiving digital datacorresponding to lung sounds detected during the inspiration andexpiration of a patient having a chest by a plurality of transducersplaced at various sites around the patient's chest; generating, inresponse to the digital data, a display on a graphical user interface,the display having a display element in which the detected lung soundsfrom a plurality of transducers are plotted in a vertically stackedconfiguration; and distinguishing the detected sounds betweeninterstitial pulmonary fibrosis and congestive heart failure.
 14. Amethod comprising: receiving digital data corresponding to lung soundsdetected during the inspiration and expiration of a patient having achest by a plurality of transducers placed at various sites around thepatient's chest; generating, in response to the digital data, a displayon a graphical user interface, the display having a display element inwhich the detected lung sounds from a plurality of transducers areplotted in a vertically stacked configuration; and dividing the datainto phases of inspiration and expiration for analysis.
 15. The methodof claim 14, wherein the dividing is performed manually by an operator.